Allplan FT 3D techniques page [revised 18.09.01]

Eyebrow dormer - this uses a technique common to most complex modelling tasks in Allplan - build a 3D solid and then convert it to reference planes.
Update 18.09.01 - following a request for a more detailed explanation I attach the reply (based on the 'Step-by-Step' guide 'Advanced 3D Modelling') at the end:

Based on project displayed on works 4 page....


draw it in 2D and then convert to 3D elements and rotate front face

 
convert combined solids to planes

The trick with the eyebrow is to draw it in 2D elevation first if you want one with a sloping top (if a horizontal top to the curve is OK then just use the dormer tool with barrel roof option in the roof modelling module) - make an outline of the front face and then the slope in elevation, convert both to 3D elements, move the front face outline so that the top is attached to the bottom of the slope line, rotate the front face 90 deg on a vertical axis and then use 'polyline sweep solid' to generate a solid of the dormer shape along the slope line. The roof solid can be generated from the normal roof plane filled with a free form wall and then converted into a 3D solid.
Based on project displayed on works 4 page....


planes will work with rafters etc.

 
with the rest of the model and wall and window inserted - note fillet of roof covering running up to cill...

To place the dormer in the correct position I refer to the 2D elevation and use parallel offset construction lines (they offset into the screen direction from any elevation view and are automatically created as 3D construction lines). Rather than try for exact snapping try to ensure a small overlap of the dormer and roof line - this should ensure that there are no 'overhangs' between the front face of the dormer and the slope of the roof solid - while it will not prevent a 'union' of the solids it will prevent them becoming a reference plane. Use the 'union' command in the 3D modelling module to join the solids and then in the 'architecture' module use '3D to planes'. Note that this command prefers that you point at the solid rather than outline it. You should now have a reference plane which you can use just the same as a normal roof plane to create rafters and roofcoverings etc. Some ingenuity is required to create an overhang of the roofcovering to the front face of the dormer - I just recessed the wall/window running under it and made a 3D 'fillet' of roofcovering to fill the gap between the bottom of the frame and the roofslope. The wall and window head will take up the shape of the dormer if the window/wall top is associated with the upper plane and the smart symbol designer will also work as normal with any opening in the wall.


Update
Reply 18.09.01 to emailed request for more detailed information on how to make this work. The page references are to the 'Step-by-Step' guide 'Advanced 3D Modelling' available from your Nemetschek Distributor
The 'hidden line image' method suggested in the SBS guide is just a suggestion of a way to create the end profile of the building in 2D - I think in fact I just drew it in 2D from scratch as it was a fairly simple outline (but see later!).
The first important part is on page 83 of the SBS - you draw the end elevation of the building which is also the side elevation of the dormer in 2D - (note that this is only necessary if the dormer is to have a sloped roof in side view - if it is level you can just use the barrel dormer tool in the roof modeller instead) - you also need to extend a couple of construction lines from the top and bottom of the side view of the dormer to allow you to draw, again in 2D, the front view of the dormer.
I experimented quite a bit with drawing the front of the dormer and gave up using the 'spline' tool and just drew one half of the dormer front view with a few straight lines which I then made curved using the 'fillet' tool to click twice on the same line and bend it - when I'd got the curve something like OK on one side of the centre line of the dormer I reflected it to ensure perfect symmetry. Remember to draw a horizontal line at the bottom joining the ends of the curves to create an enclosed shape.
Once you have a drawing similar to the setup on page 83 you need to convert the 2D lines of the dormer shape and ridge line (only) into 3D ones as described on page 84. Once they are 3D lines you move the front view of the dormer into correct position on the roof slope - as illustrated on page 84. You then need to '3D rotate' just the front view of the dormer about the y axis so that it is now in the correct relationship with the roof slope as shown on page 84.
You then need to rotate the dormer assembly of 3D lines 'up' off the 'floor' as it were by 3D rotating about the x axis - as shown on page 85. If you Delete all 2D lines in the drawing you should be left with the front face of the dormer as a 3D line and a 3D line attached to the top of the curve as per the illustration on page 85.
Now you can see why they suggested using a wireframe of the building end elevation to make the 2D outline - the 3D lines will be correctly positioned in relation to the actual 3D model (which has been in a separate drawing file 'turned off' for the moment) - at least in elevation if not in plan. If you just start off drawing it anywhere (as I did) then some playing about in the various views is necessary to line up the dormer correctly with the roof line.
In the SBS they seem to use the original building model (? not sure - they would have had to move the 3D dormer and the building into the same drawing file?) but I think I used a copy of the building or also made the 2D outline of the building end elevation previously described into 3D lines and extruded them to make a solid building and roof at this point.
Once you have got the dormer 3D lines outline into the correct position you sweep the front face back along the dormer ridge line as shown on page 86.
Now before you use the 'union' command to join the solids into one object it is critical to the eventual success of the whole operation that you zoom right in - in end elevation view - to the junction of the dormer solid with the roof slope - and check for any gaps. If the dormer solid does not meet exactly with the roof slope solid (I actually let it overlap with the roofslope solid fractionally just to be sure) , no matter how tiny the gap, it will not prevent the union of the solids but it will stop conversion to planes later on. ( A general rule of conversion of solids to planes is that 'overhangs' anywhere in the solid prevent conversion to planes).
Assuming all goes well and you can convert the solid to planes it is then just a question of how you work the plane in with your model - I tend to use multiple copies of roof planes in separate drawing files to prevent interaction of overhangs but if it was a simple building then this plane just created could be used as is for the roof.
   

 

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